first of tell as what part you didnt understandTriggers are like special type of stored procedures which will get executed in response to an event (DML/DDL/LOGON). You may right logic you want inside it which needs to be executed in response to each of the action. Also for DML trigger you can also control when it need to get executed (before or after the event designated by AFTER and INSTEAD OF triggers) and defined for each of the events (INSERT/UPDATE/DELETE). DML triggers work by means of two internal temporary tables INSERTED and DELETED which assume the structure of table on which trigger is defined.INSERTED will contain values which are inserted in case of INSERT operations and modified values in case of UPDATE operationsDELETED will contain values which are deleted in case of DELETE operation and old values in case of UPDATES